Encryption Keys Distribution for Conditional Access Software in TV Receiver SOC

ABSTRACT

A method for securely generating and distributing encryption keys includes generating, by a secured server, a pair of keys including a first key and a second key and providing, by a key distributing unit, the first key to a first recipient and a second key to a second recipient. The first recipient may use the first key to encrypt a data file and send the encrypted data file via a non-volatile memory device to a target subscriber. The second recipient may program the second key into an one-time-programmable register contained in a secure element during a manufacturing process. The secure element may further include a random access memory configured to store an image of the encrypted data file, a read-only memory containing a boot code, and a processing unit coupled to the random-access memory and the read-only memory and operative to decrypt the encrypted data file.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims benefit under 35 USC 119(e) of U.S.provisional application No. 61/372,390, filed Aug. 10, 2010, entitled“Control Word Obfuscation in Secure TV Receiver”, the content of whichis incorporated herein by reference in its entirety:

The present application is related to and incorporates by reference theentire contents of the following US applications:

-   U.S. application Ser. No. 13/021,178, filed Feb. 4, 2011, entitled    “Conditional Access Integration in a SOC for Mobile TV    Applications”;-   U.S. application Ser. No. 13/026,000, filed Feb. 11, 2011, entitled    “RAM Based Security Element for Embedded Applications”;-   U.S. application Ser. No. 13/041,256, filed Mar. 4, 2011, entitled    “Code Download and Firewall for Embedded Secure Application”;-   U.S. application Ser. No. 13/072,069, filed Mar. 25, 2011, entitled    “Firmware Authentication and Deciphering for Secure TV Receiver”;-   U.S. application Ser. No. 13/075,038, filed Mar. 29, 2011, entitled    “Generation of SW Encryption Key During Silicon Manufacturing    Process”; and-   U.S. application Ser. No. 13/076,172, filed Mar. 30, 2010, entitled    “Control Word Obfuscation in Secure TV Receiver”.

BACKGROUND OF THE INVENTION

Embodiments of the present invention relate to the field of encryptionkey distribution. More particularly, embodiments of the presentinvention relate to a system, apparatus and method for securelydistributing encryption keys for conditional access software in TVreceiver systems.

Various contents such as movies, music, game software, sport events, andothers are offered by service providers through a variety of wired andwireless communication networks. Some of these contents are encrypted sothat they can be accessed or viewed by subscribers who are in possessionof a corresponding decryption key. It is understandable that serviceproviders will try to generate encryption keys and distribute the keysin a secure manner. An encryption technique is the use of asymmetric keyalgorithms, where the key used to encrypt a widely distributed softwarecomponent (e.g., firmware) is not the same as the key used to decryptit. Embodiments of the present invention relate to an encryption keydistribution and may apply to conditional access systems for digitalbroadcast television.

There are several well-known digital radio and digital TV broadcaststandards. In Europe, the digital radio broadcast is the DAB (DigitalAudio Broadcasting) adopted by the ITU-R standardization body and byETSI. The digital TV standard is DVB (Digital Video Broadcasting) inEurope, ATSC (Advanced Television Systems Committee) in the U.S., andISDB (Integrated Services Digital Broadcasting) in Japan and SouthAmerica. In addition to these standards, there are also mobile TVstandards which relate to the reception of TV on handheld devices suchas mobile phones or the like. Some well-known mobile TV standards areDVB-H (Digital Video Broadcasting-Handheld), CMMB (China MultimediaMobile Broadcasting), and DMB (Digital Multimedia Broadcasting).

In most digital TV broadcasting services, the service providers scrambleand encrypt the transmitted data streams to protect the broadcastedcontent and require their customers or users to install “securityprotection” mechanisms to decrypt and descramble the content. Securityprotection mechanisms such as digital rights management enable users tostore content. Conditional access (CA) systems are other securityprotection mechanisms that allow users to access and view content butmay or may not record the viewed content.

In a typical pay-TV system, the conditional access software runs on adedicated secure element implementing robust mechanisms so as to preventa malicious entity (“hacker”) from gaining access to the broadcastsystem secret to decipher the TV content. The CA instruction code andkeys provisioned by the CA provider adapted to ensure security aretypically stored in the discrete secure element. The communication linkbetween the discrete secure element and the demodulator, if notprotected, presents a vulnerable entry point for hackers to get accessto the software or introduces malicious code to the TV system.

FIG. 1 is a block diagram of a conventional TV receiver 100 performingconditional access (CA) functions. Receiver 100 includes a TVdemodulator 110 coupled to a suitable antenna 105 for receivingbroadcast content. The broadcast content may be encrypted by a controlword (CW). Demodulator 110 is connected to a dedicated secure element120 via a communication link 150. Communication link 150 can be aproprietary interface or a standard interface. Secure element 120 may beprovided by the service provider and controls access to a broadcastservice by providing one or more control words to the demodulator viathe communication link. Secure element 120 may include a CPU coupled toa memory unit which may contain EEPROM and/or ROM. Secure element 120may also hold service entitlement information controlled by the serviceprovider. The service provider may communicate with the secure elementusing encrypted messages that carry descrambling keys and other servicemanagement information.

Demodulator 110 receives the code word from the secure element and usesthe code word to descramble the encrypted content. The clear stream isthen provided to a video and audio decoder 130. A display 140 coupled tothe video and audio decoder displays the decoded video and audio datastreams. In general, secure element 120 may be provided in several formsand in multiple packaging options. For example, the secure element maybe a dedicated surface mount device mounted on the receiver, a SIM card(e.g., in the context of a mobile phone), a secure SD card, or a module.

Because the communication link between the secure element and thedemodulator is not secure, an additional layer, typically a softwarelayer, is used to encrypt messages between the secure element and thedemodulator. However, hackers or attackers may get access to thissoftware layer through the communication link, and with it gain accessto the code word. Therefore, the software layer must be made protected.

It can be seen that the conventional secure element has a hardwarestructure that does not provide flexibility because it requires adedicated module and a hardware connection to the demodulator.Furthermore, conventional techniques do not appear to address theconcerns of service providers, CA operators, and content owners, namely,to provide security to the operation of their devices and the protectionof their broadcast contents.

There is therefore a need to provide systems and methods to securelydistribute the encryption keys to device manufacturers and firmwareproviders when a service provider does not have direct control to thedevice manufacturing process and firmware provision but still preventunauthorized users to gain access to the broadcast services andcontents.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention provide a system and method ofgenerating and distributing encryption keys to authorized recipients.The system includes a secured server that generates a unique pair ofkeys including a first key and a second key and a key distribution unitconnected to the secured server for transmitting the first key to afirst recipient and a second key to a second recipient. The firstrecipient may use the first key to encipher (encrypt) a data file andsend the encrypted data file via a non-volatile memory device to atarget subscriber. The second recipient may program the second key intoan one-time-programmable register contained in a secure element during amanufacturing process. The secure element may further include a randomaccess memory configured to store an image (copy) of the encrypted datafile, a read-only memory containing a boot code, and a processing unitcoupled to the random-access memory and the read-only memory andoperative to decipher (decrypt) the encrypted data file. In anembodiment, the first recipient may be a conditional access firmwareprovider, and the second recipient may be an original designmanufacturer, an original equipment manufacturer, or a devicemanufacturer that makes the secure element and sent it to the targetsubscriber. In an embodiment, the secured server may be operated by aservice or content provider.

Embodiments of the present invention also disclose a method for securelygenerating and distributing encryption keys. The method includesgenerating, by a secured server, a pair of keys including a first keyand a second key and providing, by a key distributing unit, the firstkey to a first recipient and a second key to a second recipient. Thefirst recipient may use the first key to encrypt a data file and sendthe encrypted data file via a non-volatile memory device to a targetsubscriber. The second recipient may program the second key into anone-time-programmable register contained in a secure element during amanufacturing process. The secure element may further include a randomaccess memory configured to store an image of the encrypted data file, aread-only memory containing a boot code, and a processing unit coupledto the random-access memory and the read-only memory and operative todecrypt the encrypted data file by executing the boot code.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention are described below, byway of example only, with reference to the accompanying drawings, inwhich:

FIG. 1 is a block diagram of a conventional TV receiver 100 performingconditional access (CA) functions;

FIG. 2 is a simplified block diagram of a receiver system on a chip(SOC) according to an embodiment of the present invention;

FIG. 3 is a simplified block diagram of a demodulator SOC having anintegrated secure element according to an embodiment of the presentinvention;

FIG. 4 is a block diagram of a TV demodulator SOC in communication withan external video and audio decoder and an external flash memoryaccording to an embodiment of the present invention;

FIG. 5 illustrates a demodulator SOC performing a firmware downloadoperation from an external memory according to an embodiment of thepresent invention;

FIG. 6 is a diagram illustrating an exemplary firmware run-timeauthentication using hardware facilities provided by the secure elementaccording to an embodiment of the present invention;

FIG. 7 a block diagram illustrating a secure generation and distributionof asymmetric keys according to an embodiment of the present invention;and

FIG. 8 is a flowchart diagram illustrating an example method ofgenerating a pair of asymmetric keys and securely providing the keys toauthorized recipients according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Conditional access is used by TV broadcasters to generate revenue. Toachieve this, security guidelines are used to protect the keysprovisioned to the user and to guarantee that no hacker or maliciousentity can crack the system and watch contents for free. Theseguidelines, also referred to as security requirements, define methodsadapted to prevent misuse of the SOC (system-on-chip) device and itsassociated firmware, and furthermore to inhibit unauthorized access tosecrets, such as keys, operating modes, etc. The SOC security frameworkdescribed herein defines hardware (HW), software (SW), or a combinationthereof (i.e., firmware) to achieve these objectives.

FIG. 2 is a simplified block diagram of a receiver system on a chip(SOC) 200 configured to perform tuning, demodulating, CA security, andthe like, in accordance with an embodiment of the present invention.Receiver system 200 includes a digital broadcast receiver 210 that maybe capable of receiving signals in a number of different frequency bandsof interest and/or in a number of different formats. By way of example,receiver system 200 may be capable of receiving any one or more of thestandards mentioned above or other suitable standards. In an exemplaryembodiment, receiver system 300 also includes a conditional accesssecurity (CAS) sub-system 250.

Digital broadcast receiver 210 includes a tuner 212 that is connected toan antenna 211. Although an antenna is shown, tuner 212 may be connectedto a number of antennas that is configured to suit different frequencybands of interest. The tuner frequency translates received signals andprovide them to a demodulator 214, which may demodulate the frequencytranslated signals into multiple data streams (audio, video, text, andothers). Receiver 210 also includes a descrambler 216 that descramblesthe data streams (indicated as encrypted TS) and provides clear (i.e.,descrambled) data streams (indicated as clear TS in FIG. 2) to a hostvia a host interface unit 218. Receiver 210 further includes a controlprocessor 220 and a memory unit 222 that contains software (programcode) to enable a user to select a service and to program the tuner to adesired frequency. In an embodiment, memory 222 may include dynamicrandom memory and/or permanent memory such as read-only memory (ROM).

Receiver 210 also includes a control interface unit 224 that connectsthe broadcast receiver 210 with the conditional access securitysub-system 250. As described in section above, control access is aprotection of content required by content owners or service providers.Conventional access approaches use dedicated surface mount devices suchas Smartcard, SIM card, secure SD card or the like. In conventionalapproaches, CA instruction code and keys provisioned by CA providersadapted to ensure security are typically stored in a non-volatilememory, such as an EEPROM or Flash, which are relatively expensive andcannot be easily and cost effectively integrated using standard CMOSfabrication processes. A novel conditional access security (CAS)sub-system according to an embodiment of the present invention will bedescribed in detail below.

Referring to FIG. 2, CAS sub-system 250 includes a secure processor 252coupled to a memory unit 254. The secure CPU may be a RISC CPUconfigured to process various processing operations. CAS sub-system 250may further include a crypto hardware 256 that, in an embodiment,includes suitable crypto logic, circuitry (e.g., hardware) forperforming cryptographic operations. In a specific embodiment, cryptohardware 256 may be a crypto processor configure to performcryptographic functions such as processing digital signature, keymanagement, identifying public keys and others due to the secure accessrequirements. During the manufacturing process, cryptographic hardwaremay generate a unique crypto ID (device identifier) for the receiver SOC200 and a unique encryption key. CAS sub-system also includes a fusebank 260. In an embodiment, fuse bank 260 may include electricallyprogrammable fuses on the chip. In an embodiment, the fuse bank maycontain an array of electrically programmable registers, each having anumber of bits. The bits can be programmed during the manufacturingprocess or later by the service provider as the device is shipped to theuser. In an embodiment, corresponding bits of the fuse bank are burnedor blown according to the value of the unique device ID and acertificate key. In a specific embodiment, memory unit 254 may includerandom access memory and read-only memory. In contrast to conventionaltechniques, memory unit 254 does not includes EEPROM and/or Flash memoryto facilitate the integration process and to minimize cost by usingconventional (i.e., standard) CMOS process.

In an embodiment, receiver SOC 200 includes an external memory interface268 configured to interface with an external memory device (not shown).The external memory may be a flash memory containing firmware orsoftware code and other associated information data that are requiredfor the receiver SOC to perform the descrambling functions. Details ofthe firmware, software code and the associated information data will bedescribed in detail in sections below. In an embodiment, the externalmemory interface 268 can include a SD memory card slot, a multimediacard (MMC), a micro SD card slot, a mini SDHC, a microSDHC, a MemoryStick slot, a PCMCIA interface, a USB interface, a serial or a parallelinterface, and others. The external memory can be a commercialoff-the-shelf Flash memory in a specific embodiment.

In accordance with embodiments of the present invention, the conditionalaccess (CA) software code is stored in a random access memory (RAM). TheCA software is dynamically downloaded from an external non-volatileflash memory via the external memory interface 268 to the RAM during thepower cycle of the security sub-system. However, because the externalflash storing the CA software is outside the security perimeter it mustfirst be authenticated and checked for any malicious alteration (such asbypass of the security function that could be inserted by a hacker). Thesecure sub-system implements a protocol to authenticate the firmwareusing a public key algorithm and digital certificate provisioned duringmanufacturing.

FIG. 3 is a block diagram of a demodulator SOC 300 including ademodulation logic 310 coupled to a remote memory device 480 (e.g.,Flash memory) and an integrated secure element 350 according to anembodiment of the present invention. Demodulation logic 310 may have asimilar configuration of the receiver 210 shown in FIG. 2. For example,demodulation logic 310 may include a demodulator, a descrambler, acontrol CPU, a memory unit that comprises RAM and/or ROM, a hostinterface, and a control interface unit; the functions of those elementshave been described in details in the sections above and won't berepeated herein for brevity. The demodulator logic 310 may furtherinclude system-on-a chip infrastructure such as registers, IO ports, anexternal memory interface link 320, which may be similar to the externalmemory interface port 268 shown in FIG. 2 and described above. In anembodiment, remote or external Flash memory 380 may be coupled to thedemodulator SOC 300 through the interface link 320. The coupling can beby means of a physical connection such as a SD card connector or a USBconnector. In another embodiment, the coupling can be by means of anoptical (e.g., infrared) or radio wave (e.g., Bluetooth, wireless LANIEEE802.11, or the like) communication link.

In an embodiment, integrated secure element 350 includes a secure CPU352, a boot read-only memory (ROM) 353, a secure random access memory(RAM) 355, multiple non-volatile memory registers (or one-timeprogrammable fuse banks) 360. CPU 352 may include an adder and logic forexecuting arithmetic operations or comparative decisions. In anembodiment, the non-volatile memory registers are implemented using fusecells that can be fabricated using standard CMOS processes. In anembodiment, the non-volatile memory registers are programmed (burned orblown) during the silicon manufacturing process to store informationsuch as the device ID, the root public key, and others. Integratedsecure element 350 also includes a hardware accelerator 356 that can beone or more crypto processors as described above in association withcrypto hardware 256 of FIG. 2.

In order to minimize cost, the CA software code is stored in the secureRAM 355 according to an embodiment of the present invention. CA softwareis understood as instructions, one or more sets of instructions, datafiles, firmware, or executable applications that are provided to thesecure CPU 352 for execution. CA software is dynamically downloaded fromthe remote (external) flash memory 380 to the RAM 355 (“RAM-ware”)during the power cycle of the integrated secure element 350. Because CAsoftware is downloaded from the external Flash memory, it must be firstauthenticated by the integrated secure element 350. In an embodiment,the secure element operates a protocol to authenticate the RAM-wareusing a public key algorithm and a digital certificate (e.g., a uniquedevice ID) that is provided during the manufacturing of the demodulatorSOC. In an embodiment, the authentication process can be assisted andaccelerated using hardware accelerator 356.

In an embodiment, CA software is received by the demodulator logic fromthe external memory and transferred to the secure RAM 355 via ademodulator interface circuit 366. In contrast to conventional secureelements that store the CA software code in EEPROM and/or

Flash memory, embodiments of the present invention provides a RAM-warearchitecture that can be updated securely and easily, e.g., bydownloading firmware (i.e., software, program codes, data files) storedin external memories. Because the external memory containing the CAsoftware is outside the security perimeter of the secure element, itmust first be authenticated. In an embodiment, the downloaded CAsoftware is authenticated by the secure element running bootauthenticate programs from the boot ROM 353. Because the RAM-warearchitecture does not require EEPROM and/or Flash memory that requiresamong other things a double poly process or a tunnel oxide process andexpensive testing equipment and procedures, the RAM-based architectureof the present invention can be cost effectively produced using standardCMOS processes.

In an embodiment, the integrated secure element produces an attributebased on a digital certificate contained in the received software (nowRAM-ware because it is now stored in the secure RAM) and provides theattribute to the demodulator logic for descrambling the received datastreams (not shown). In some embodiments, the attribute can be a securebit pattern or a secure codeword to enable the descrambling process inthe demodulator logic 310.

In an embodiment, the integrated secure element 350 is activated whenthe TV application is enabled by the user. When the TV application isenabled, the demodulator logic causes the boot ROM to execute the bootinstructions and activate the integrated secure element. During the bootprocess, the conditional access (CA) firmware stored in the externalflash memory is downloaded to the RAM disposed in the secure element, sothat the CPU starts operating.

As described above, the remote Flash memory contains conditional access(CA) executable applications or data files that are dynamically loadedto the RAM 355 disposed in the integrated secure element. In anembodiment, the external memory contains a digital certificate that isgenerated by the CA vendor or the demodulator SOC device manufacturerand signed with the root private key or a derivative of the root keyusing public key infrastructure (PKI). In an embodiment, the digitalcertificate may be unique to each demodulator SOC device and contains adevice identification (ID) code. In an embodiment, the sameidentification code may also be stored in one or more of thenon-volatile registers 460. In an embodiment, the non-volatile memoryregisters 360 may also store a digital signature of the CA software orCA firmware. In an embodiment, the boot ROM authenticates the CAfirmware by means of the digital certificate.

In an embodiment, the secure boot ROM may process the digitalcertificate as follows: (i) verify that the certificate is authentic andthe certificate has been signed by a trusted delegate of the root keyowner; (ii) verify that the certificate is intended for the given deviceby comparing the device ID stored in the secure element NVM(non-volatile memory) registers and the code stored in the certificateto ensure that they match; and (iii) authenticate the firmware byregenerating its signature with the root public key and comparing theresult with the value stored in the certificate. Only when the abovethree steps are successful, the SW that has been downloaded to thesecure element RAM is verified and considered to be trustworthy. In anembodiment, the SW code in the external memory may be encrypted. In thiscase, it is first deciphered by the boot ROM. The SW encryption key (ora derivative) is stored in the secure element NVM registers and useddirectly by the ROM code.

FIG. 4 is a block diagram of a TV demodulator SOC 400 in communicationwith an external video and audio decoder 470 and a flash memory 480according to an embodiment of the present invention. As shown, the TVdemodulator SOC includes a tuner and demodulator 410 coupled to anantenna 405 for received a desired modulated content that may beencrypted. TV demodulator SOC 400 may include a demodulator CPU 420 forcommunicating with a user and for controlling the tuner demodulator.Demodulator CPU 420 is coupled to a memory unit 430 that may containstatic random access memory and read-only memory. TV demodulator SOC 400also includes a descrambler 440 that is configured to received anencrypted data stream 412 from the tuner and demodulator 410 using anencryption key or a control word delivered from a secure elementsub-system. In contrast to a conventional conditional access system, thesecure element sub-system is integrated within the TV demodulator SOC.The secure element sub-system includes a secure CPU 452 coupled to aread-only memory ROM 456 and a secure random access memory RAM 456. Incontrast to the conventional access system that contains flash memory orEEPROM for storing boot loader firmware, TV demodulator SOC does notinclude flash memory or EEPROM, so that TV demodulator SOC can befabricated using cost effective standard CMOS processes that do notrequire special floating gate processes and associated testing steps.

TV demodulator SOC receives a firmware image (i.e., data representativeor a copy of the firmware disposed in an external device. The termfirmware and firmware image will be used alternatively hereinafter) fromexternal flash memory 480 via a memory interface port 420. The firmwaredownload can be, for example, initiated by the demodulator CPU 420 andstored in the secure RAM 456. Because the flash memory is external tothe TV demodulator SOC and thus to the secure element sub-system, thefirmware image (i.e., a copy of the firmware) must be firstauthenticated by the secure element sub-system before being executed.Upon a successful authentication, the secure element sub-system willexecute the firmware image to produce a control word or encryption keyfor the descrambler to decipher the encrypted data stream. The controlword is transmitted to the descrambler through a physical link 442 thatmust be protected from hacking Details of the firmware download from theexternal flash memory, the authentication process and the protection ofthe control word through obfuscation will be described in more detailbelow.

The descrambler deciphers the encrypted data stream and produces a cleardata stream to a video and audio decoder 470 that is coupled to adisplay unit 475 for reproducing the video and audio content.

FIG. 5 illustrates a demodulator SOC 500 performing a firmware downloadoperation from an external memory according to an embodiment of thepresent invention. Demodulator SOC 500 comprises a demodulator logic 510and an integrated secure element 550. Demodulator logic 510 may includea tuner, a demodulator, a descrambler, control CPU, a memory unit, ahost interface as shown in FIG. 2. The demodulator logic may include SOCinfrastructure having one or more IO ports, a memory interface unit, andothers. In an exemplary embodiment, the SOC infrastructure may includean interface unit 512 such as a USB, a peripheral computer interface(PCI), a SD (secure digital) interface, or a communication link forinterfacing with an off-chip non-volatile memory 580. In a specificembodiment, interface unit 512 may establish a connection to the remotememory via a short distance physical connection by means of a USBconnector, an SD connector, or the like. In another embodiment, theinterface unit 512 may coupled to the remote NVM memory 580 via a localarea network, a personal area network (Bluetooth) or a wireless areanetwork according to the IEEE802.11 standard or the like (the local,personal, or wireless area network is indicated as a cloud 570).

The integrated secure element includes a secure CPU 552 that togetherwith a boot ROM 554 initiates the integrated secure element at power up.The secure element further includes a secure random access memory(S-RAM) 556, one or more hardware accelerators 558, one or morenon-volatile memory (NVM) registers or fuses 560, and a slavedemodulator interface circuit 562 that couples the integrated secureelement 550 with the demodulator logic 510.

The secure element may include a firewall 564 that allows for the secureCPU to initiate a connection to the remote memory 580 and downloadfirmware (i.e., data files, executable applications) 582 from the remotememory to the secure S-RAM 556, but does not allows the remote memory toinitiate a connection in the reverse direction.

After clearing the content of secure S-RAM 556, the demodulator SOC mayinitiate a download of firmware 582 from remote flash device 580. Thedownload process can be performed by the demodulator CPU D-CPU by meansof the hardware master port and send the firmware to the secure S-RAMthrough slave port interface 562. However, this read-and-write of the CAfirmware from the remote flash memory cannot be considered as securebecause demodulator logic 510 and remote flash memory 580 are outside ofthe secure element boundary. Therefore, the downloaded firmware image inthe secure S-RAM must be authenticated to protect the firmware imagefrom modification. Once the firmware image download is complete, thesecure element locks the slave interface and the firewall to prevent anysubsequent access from the non-trusted demodulator interface and secureS-CPU 552 may start executing from boot ROM 554. It is noted that thedemodulator logic cannot access secure element 550 through master-slavedemodulator interface 562 once the security element is locked.

FIG. 6 is a diagram illustrating a firmware run-time authentication 600using hardware facilities provided by the secure element according to anexemplary embodiment of the present invention. Firmware run-timeauthentication 600 is an exemplary embodiment providing an efficient wayto mitigate the risk of running malicious code at run time. The firmwarerun-time authentication verifies and authenticates software within powercycles to protect hardware intrusive attacks and fault injection. In anembodiment, the hardware facilities of the secure element writes(programs by burning or blowing fuses) a software checksum SWChecksum608 to one or more of the NVM registers 628 during the boot process andwrites runtime configuration parameter to corresponding configurationregisters of the secure element finite state machine 668, which controlsthe cryptographic hash function 612 and the comparator 618.Cryptographic hash function 612 produces a hash value HV18 from firmware610 and compares (618) the hash value HV18 with the SWChecksum stored inone of the NVM registers 628. In the event that there is a match(indicated as “Yes”), the secure element continues its operation. In theevent there is no match (indicated as “No”), i.e., the firmware may havebeen modified or compromised, the secure element disables the firmwareexecution. In some embodiments, the firmware run-time authentication canbe triggered from different sources that may include, but is not limitedto: 1) software driven by requesting an authentication through a controlregister in the security element; 2) hardware timer as a recurring eventdriven by a hardware counter set during the boot process; 3) when thesecure S-CPU enters or exits a sleep period; or 4) when the secure S-CPUreceives a wakeup request.

In an embodiment, the hash value of the decrypted firmware is stored inthe boot certificate and is programmed into one of the NVM(one-time-programmable) registers in the secure element during the bootprocess so that it cannot be modified or altered. It is important tonote that this process cannot be performed by the RAM-ware itselfbecause the RAM-ware can be tampered with. Thus, the process has to beperformed entirely in hardware or using code stored in ROM that cannotbe modified. The SWchechsum written into a write-once memory registercan be reset on power-on/off of the secure element. In addition, thesecure element includes control parameters that define the source andrecurrence of the run-time check.

In an embodiment, certificate 601 may include runtime configuration data602 that is written into associated configuration registers 669 of thesecure element. Configuration data 602 may configure or customize thefinite state machine (FSM) so that the secure element operates in amanner that is desired by a vendor or a service provider. In thisexample embodiment, the secure element may start executing the firmwarein the secure RAM upon a successful authentication. The execution of thefirmware may include generating a control word and provide it securelyto the demodulator for deciphering encrypted data streams.

Embodiments of the present invention include a secure generation anddistribution of a pair of encryption keys by a secured server. A firstencryption key may be sent to a first recipient that uses the firstencryption key to encipher (encrypt) a data file before distributing itto a target subscriber. The second encryption key is sent to a secondrecipient that may program the encryption key into a secure elementduring the manufacturing process. The secure element will use the storedkey to decipher (decrypt) the encrypted data file received from thefirst recipient. The pair of encryption keys may be unique to the secureelement. That is, each target subscriber may receive a secure elementhaving a unique private key for deciphering the encrypted data file.

FIG. 7 a block diagram illustrating a system and method for securelygenerating and distributing a pair of asymmetric keys according to anembodiment of the present invention. In an embodiment, the secure keydistribution system includes a secured server 701 for generating andstoring a pair of keys including a private key 702 and a public key 703.A key distribution unit 704 is coupled to secured server 701 andprovides the private key to an original design manufacturer (ODM), anoriginal equipment manufacturer (OEM), or a device manufacturer 710 andthe public key to a firmware provider. The key distribution system inreference to FIG. 7 may be used by a service provider or a contentprovider that teams up with a device manufacturer, an ODM or an OEM toprovide secure devices to target subscribers for accessing broadcastservices and contents. The service provider also may team up with aconditional access (CA) firmware provider for creating firmware for theoperation of the secure devices. In an embodiment, the service orcontent provider may operate the secured server 701 that iscommunicatively connected to the device manufacturer through a keydistribution unit 704. In an embodiment, the communication between thedevice manufacturer and the key distribution unit is via a securecommunication link 712. In an embodiment, the device manufacturer maysend a request to the secured server for obtaining a private key. Inreply to the request, the secured server may send the private key to thedevice manufacturer via the secure communication link 712. In anembodiment, the secure communication link 712 may be a secure socketslayer (SSL) link. In an embodiment, the key distribution unit 704 mayperform functions associated with conventional communication systemssuch as authentication the request by the user identity and the passwordand the like and management of the communication traffic between thesecured server and the requester. In another embodiment, the devicemanufacturer may operate the secured server to generate the private andpublic keys and provides the public key to the CA firmware provider viathe key distribution unit.

In an embodiment, firmware provider receives the public key sent by thekey distribution unit and encrypts (724) a clear firmware 720 using thereceived public key to produce an encrypted firmware 726. In anembodiment, the clear firmware 720 may includes a conditional accessfirmware for distributing to target subscribers. In an embodiment, theclear firmware 722 can be encrypted using the RSA algorithm. In anembodiment, the encrypted firmware 726 can be stored in a non-volatilememory device 780 for sending to target subscribers.

Still referring to FIG. 7, device manufacturer (ODM, OEM) 710 mayproduce a receiver system on a chip (SOC) as shown and described in FIG.2, a demodulator SOC as shown and described in FIG. 3, or a demodulatorshown an described in FIGS. 4 and 5. For the sake of brevity, only partsof the SOC that are used for the decryption of the encrypted firmwarewill be described below. SOC 750 may includes a secure CPU 752 that iscoupled to a boot ROM 754 and a secure random access memory (RAM) 756.SOC 750 also includes a non-volatile register which can be an one-timeprogrammable array of fuses or a secure flash register for storing thereceived private key. It is noted that the programmed private key in thenon-volatile register or the one-time programmable array of fuses is notaccessible externally once programmed. Other precautions can be taken tohide or obfuscate the stored private key.

SOC 750 may include a decryption module 754 that can be acrypto-processor, hardware logic, or a dedicated deciphering hardwareand software to decrypt the encrypted firmware 726 contained in theremote non-volatile memory 780. In an embodiment, the decipheringprocess (decryption module 754) decrypts the encrypted firmware usingthe RSA algorithm. The clear (i.e., decrypted) firmware is then storedin secure RAM 756. In an embodiment, the clear firmware is authenticatedprior to being stored in the secure RAM or executed by CPU 752.

In an embodiment, SOC may download the encrypted firmware 726 via acommunication network 720 that is disposed between the firmware providerand the SOC 750. Communication network can be one of the local areanetwork, a metropolitan area network, a wide area network, or a wirelessor cellular network.

FIG. 8 is a flow diagram of an example method 800 of generating a pairof asymmetric keys and securely providing the keys to authorizedrecipients according to an embodiment of the present invention. Thisflow diagram is merely an example, which should not unduly limit thescope of the claims herein. One of ordinary skill in the art wouldrecognize other variations, modifications, and alternatives. Forexample, one or more steps can be provided in a different sequencewithout departing from the scope of the claims herein. In step 802, asecured server generates a pair of asymmetric keys including a publickey and a private key that are then provided to authorized recipients.It is appreciated that the public and private keys are unique for theauthorized recipients and thus provide a robust binding mechanismbetween the authorized recipients. In step 804, a key distribution unitthat is communicatively connected to the secured server sends the publickey to a first recipient via a first communication link. In anembodiment, the first recipient may be a conditional access firmwarevendor that uses the received public key to encrypt a firmware (step808) prior to distributing it to target subscribers. In an embodiment,the encrypted firmware may be stored in a non-volatile memory devicesuch as a CD-ROM or a flash memory device for distribution. In anotherembodiment, the first recipient may make the encrypted firmwareaccessible or downloadable via the Internet. In step 806, the keydistribution unit sends the private key to a second recipient via asecond communication link. The second recipient can be a devicemanufacturer, an ODM, or OEM that programs the received private key intoa non-volatile register that can be an one-time programmable array offuses or a secure flash register in a secure element of asystem-on-a-chip demodulator or receiver. At step 810, the secondrecipient programs the received private key in a secure element of theSOC demodulator or receiver. The programming may be performed by burningor blowing a number of fuses during the manufacturing process of thesecure element in a preferred embodiment. At step 812, the secureelement may download the encrypted firmware either from a remotenon-volatile memory device or via the Internet from the first recipient.In step 814, the secure element deciphers the encrypted firmware usingthe private key contained in its one-time programmable fuse array.

It is to be understood that the above description is intended to beillustrative and not restrictive. Many embodiments will be apparent tothose of skill in the art upon reviewing the above description. Thescope of the invention should, therefore, be determined not withreference to the above description, but instead should be determinedwith reference to the appended claims along with their full scope ofequivalents.

1. An encryption key distribution system comprising: a secured serverconfigured to generate at least one pair of keys including a first keyand a second key; a key distribution unit operably coupled to thesecured server; a first recipient configured to receive the first keythrough the key distribution unit and encrypt a data file using thefirst key; and a second recipient configured to receive the second keythrough the key distribution unit and program a secure element; whereinthe secure element comprises: at least one non-volatile registerconfigured to store the second key; a random access memory configured tostore an image of the encrypted data file; a read-only memory includinga boot code; and a processing unit coupled to the read-only memory andthe random access memory and being operative to decrypt the image of theencrypted data file using the second key.
 2. The encryption keydistribution system of claim 1, wherein the first key and the second keyare different.
 3. The encryption key distribution system of claim 1,wherein the first recipient is a conditional access software providerand the second recipient is a original design manufacturer (ODM) or aoriginal equipment manufacturer (OEM).
 4. The encryption keydistribution system of claim 1, wherein the second recipient isconnected to the key distribution unit via a secure communication link.5. The encryption key distribution system of claim 4, wherein the securecommunication is a secure sockets layer (SSL) link.
 6. The encryptionkey distribution system of claim 1, wherein the second key is programmedinto the at least one non-volatile register during a manufacturingprocess of the secure element.
 7. The encryption key distribution systemof claim 1, wherein the secured server is operated by a serviceprovider.
 8. The encryption key distribution system of claim 1, whereinthe secure element receives the encrypted data file from the firstrecipient via the Internet.
 9. The encryption key distribution system ofclaim 1, wherein the secure element receives the encrypted data filethrough an external non-volatile memory device.
 10. An encryption keydistribution method comprising: generating, by a secured server, atleast one pair of keys including a first key and a second key;providing, by a key distribution unit, the first key to a firstrecipient, encrypting a data file by the first recipient using the firstkey; providing, by the key distribution unit, the second key to a secondrecipient; and programming, by the second recipient, the second key in asecure element; wherein the secure element comprising: a non-volatileregister configured to store the private key; a random access memoryconfigured to store an image of the encrypted data file; a read-onlymemory including a boot code; and a processing unit coupled to theread-only memory and the random access memory and being operative todecrypt the image of the encrypted data file.
 11. The encryption keydistribution method of claim 10, wherein the first key and the secondkey are different.
 12. The encryption key distribution method of claim10, wherein the first recipient is a conditional access softwareprovider and the second recipient is a original design manufacturer(ODM) or a original equipment manufacturer (OEM).
 13. The encryption keydistribution method of claim 10, wherein the second recipient isconnected to the key distribution unit via a secure communication link.14. The encryption key distribution method of claim 12, wherein thesecure communication is a secure sockets layer (SSL) link.
 15. Theencryption key distribution method of claim 10, wherein the second keyis programmed into the non-volatile register during a manufacturingprocess of the secure element.
 16. The encryption key distributionmethod of claim 10, wherein the non-volatile register is an one-timeprogrammable register comprises a plurality of fuses.
 17. The encryptionkey distribution method of claim 10, wherein the secured server isoperated by a service provider.
 18. The encryption key distributionmethod of claim 10 further comprising sending the encrypted data file,by the first recipient, to the secure element via an externalnon-volatile memory device.